Modoc Rock Shelter, beneath the sandstone bluffs near Prairie du Rocher in southwestern Illinois, preserves more than 28 feet of sediment and evidence of repeated Native American occupation over thousands of years. Its layers show changing uses during the Archaic period, from a short-term hunting camp about 9,000 years ago, to a longer-term base camp for several families about 6,000 years ago, and later a temporary hunting camp again around 4,000 years ago. Artifacts and animal remains reveal domestic life, toolmaking, and diet. Identified by archaeologists after a 1951 discovery and later excavated extensively, it became a landmark site for understanding deeply stratified Archaic cultures in the eastern United States.